Sensor element

Abstract

A heater part of a planar sensor element includes: a Pt heater element; and an insulating layer including 90-99.9 wt % of an insulating material having a different coefficient of thermal expansion from a solid electrolyte forming a base part of the element. The heater part other than a heater electrode is buried in the base part. The heater element has a thickness of 10-50 μm and is covered with the insulating layer. The insulating layer has a porosity of 4% or less and a thickness of 50-150 μm. The distances of the insulating layer from an end portion of the element, from a main surface on which the heater electrode is located, and from a side surface of the element are respectively 0.25-0.75 mm, 0.20-0.60 mm, and 0.20-0.60 mm. The total length of the element is 80.0 mm or less.

Description

BACKGROUND OF THE INVENTIONField of the Invention[0001]The present invention relates to a sensor element formed of an oxygen-ion conductive solid electrolyte, and, in particular, to the configuration of a heater included in the sensor element.Description of the Background Art[0002]As an apparatus for measuring the concentration of a predetermined gas component (e.g., O2, NOx, HC, and CO) in a measurement gas, including a combustion gas and an exhaust gas in an internal combustion engine, such as an engine of a vehicle, a gas sensor including a sensor element formed of an oxygen-ion conductive solid electrolyte, such as zirconia (ZrO2), has been known.[0003]As such a sensor element of the gas sensor (gas sensor element), a sensor element having a structure in which a sensor part for performing detection of a target gas component and the like and a heater part including a heater for heating the sensor part to activate the oxygen-ion conductive solid electrolyte forming the sensor part...

AI Technical Summary

Benefits of technology

[0015]According to the present invention, when the sensor element is used continuously, and a temperature cycle including heating during use and cooling after use is repeated, diffusion of Pt and the occurrence of cracking caused by a difference in coefficient of thermal expansion between solid electrolyte layers and a heater insulating layer are suitably prevented or reduced, enabling the planar sensor element to have an increased lifetime.

[0016]An object of the present invention is thus to provide a sensor element having an increased lifetime due to prevention or reduction of diffusion of Pt during use and prevention or reduction of the occurrence of cracking caused by a difference in coefficient of thermal expansion between solid electrolyte layers and an insulating layer.

Problems solved by technology

However, in the case that a conventional sensor element including a heater that includes a heater element formed of Pt and a porous insulating layer is used continuously while setting the driving temperature to a relatively high temperature of approximately 850° C., a problem in that a heater resistance value increases over time to eventually disable the sensor element is more likely to occur compared with a case where the driving temperature is low.

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